Well first you have to install Arduino 1.8.9 here. Has to be that version.
Go to this site and click on on green download button. Save the file to desktop or somewhere easy to remember finding.
If you don’t already have an archiver program, I recommend dowloading and installing 7zip or winrar.
Once all the above is done, use the archiver program to extract files to desktop.
You will need to open and find the Marlin.INO file. This will bring up a Folder called Marlin-MPCNC_MRambo_T8_16T_LCD. (Bugfix 2.0.x didn’t work) Open that, then open the folder name Marlin, you should see a Marlin, with blue round icon. That is the one you want to open in Arduino, which can be done in Arduino or by double clicking it.
Then you have to follow instructions posted here, scroll down to how to flash the board section of the page follow steps closely. I chose configuration_h tab in Arduino program. Once it say done uploading with no errors, you can connect the LCD screen but make sure you are putting the right connectors on and in the right direction.